This invention relates to a process for the preparation of mixed partial esters of carbohydrates, particularly of monoses or oligosaccharides or their cleavage products, and hydrolysis products of polysaccharides.
It is an object of the invention to produce interfacially-active substances from readily accessible starting materials by a simple process requiring little technical or economic outlay, and at the same time to obtain products, which after use, can be completely degraded biologically.
It has been proposed to produce partially acetylated saccharides having on average 5 acetyl groups per molecule in aqueous solution by means of an organic extraction agent, the resulting products being satisfactorily interfacially-active
It is an object of the invention to produce still lower-acylated carbohydrates which are modified by the introduction of fatty acid radicals and which are particularly suitable as detergent substances. Exhaustive tests have shown that novel interfacially-active mixed partial esters can be obtained without the additional use of organic solvents by a very simple process.
Individual mixed esters of sugars with higher and lower fatty acids which can be obtained by esterification of a carbohydrate-containing starting material with higher and lower fatty acids or fatty acid anhydrides in the presence of acid catalysts are known per se, but these mixed esters are completely or highly esterified carbohydrates the special properties of which (resistance to heat and hydrolysis, water-repellent action) make them suitable as plasticizers, film-forming agents, waterproofing agents or oil additives in internal combustion engines, but not as interfacially-active agents.
In contradistinction to this, a feature of the present invention is the preparation of only low-acylated mixed esters of the said carbohydrates having outstanding interfacially-active properties. In this connection it was found that the conversion of the carbohydrate starting material to an ester having only a low acyl number produces a product which, together with a lower-aliphatic acylation agent, serves as a solvent both for the carbohydrate starting material and for a higher fatty acid component. A prerequisite to this double function is that, for example, in the case of saccharose, acylation with the lower-aliphatic acylation agent should be carried out only to a low acylation number, usually a maximum of one hydroxyl group out of the three primary hydroxyl groups, for the esterification with the lower-aliphatic acylation agent, so that there remains a maximum of two hydroxyl groups available for the esterification with the higher fatty acid radical.